the fate of chemically dispersed and untreated crude oil

VOL. 40, SUPP. 1 (lS87) P. 149-161 ARCTIC

The Fate of Chemically Dispersed and Untreated Crude Oil in Arctic Benthic Biota

B. HUMPHREY,’ P.D. BOEHM,’ M.C. HAMILTON’ and R.J. NORSTROM3

(Received 3 July 1986; accepted in revised form 28 April 1987)

ABSTRACT. Subtidal benthic biota were monitored for petroleum hydrocarbons following two experimental oil spills at Cape Hatt, N. W .T., Canada. In one spill oil was chemically dispersed into the water column, and in the other oil was released onto the water surface and allowed to strand on the shoreline. In addition to baseline samples, samples were collected immediately after the oil releases, two to three weeks after and one and two years after. Initial observations did not distinguish between effects of the surface and dispersed releases. Total oil content and hydrocarbon compositional analyses were conducted to investigate patterns of uptake and depuration for five different arctic species: Asrurre boreulis, Mucom culcareu, Myu rruncuru, Serripes groenlundicus and Strongylocentrorus droebuchiensis. Filter-feeding species took up oil rapidly from the water column, while deposit-feeding species took up oil less rapidly from the sediments. All species depurated most of the oil after one year, but after two years the deposit feeders appeared to be taking up more oil from sediments contaminated by stranded oil from the surface oil release. Key words: oil, petroleum, determination, benthos, weathering, degradation, depuration, Arctic

&SUMI?. On a recherche la pdsence d’hydrocarbures p6troliers dans le biote benthique sous le niveau des m d e s , B la suite de deux dkversements exp6rimentaux de p6trole au cap Hatt (T. N.-O.), au Canada. Pour un des deversements, on a disperd le fitrole chimiquement dans la colonne d’eau, et pour l’autre, on l’a dpandu en nappe B la surface et on l’a laisd s’khouer sur le rivage. En plus des dchantillons temoins, on a pdlevb des khantillons tout de suite ap&s les deversements, de deux B trois semaines plus tard, ainsi qu’un an et deux ans ap&s. Lors des observations initiales, on n’a pas cherche B faire la difference entre les effets du deversement en surface et ceux du fitrole disped. On a fait des analyses de la teneur totale en hydrocarbures et de leur composition, pour ttudier les mecanismes d’absorption et de depuration de cinq es@ces arctiques diffkrentes: Asrurre boreulis, Mucom culcareu, Myu rruncuru, Serripes groenlundicus et Strongylocenrrorus droebuchiensis. Les espkes filtreuses ont absorbe rapidement le p6trole B partir de la colonne d’eau, tandis que les esgces dkpositivores l’ont absorbe moins rapidement B partir des sediments. Toutes les es@ces ont rejet6 la plupart du fitrole au bout d’un an, mais ap&s deux ans, les es@ces depositivores semblaient encore absorber du p6trole B partir des sediments pollues par le p6trole tchoue provenant de la nappe deverde en surface. Mots c h : Htrole, petroliers, determination, benthos, degradation, d&omposition, &puration, arctiques

Traduit pour le journal par Ntsida Loyer.

INTRODUCTION

The Baffin Island Oil Spill (BIOS) Project assessed the use of chemical dispersants on an oil slick in the arctic nearshore by comparing the fate and effects of chemically (Corexit 9527) dispersed oil to the fate and effects of an untreated surface oil slick left to natural cleaning processes. Chemical dispersion has been used as an oil spill countermeasure to protect sensitive environments in temperate regions of the world (Nichols and Parker, 1985; Lindblom et al., 1981). A study of dispersion effect and effectiveness was conducted in Searsport, Maine, around the time of the BIOS experiments (Gilfillan et al., 1985). However the significance of the BIOS Project was the use of dispersants in the arctic environment.

The project rationale and design are described by Sergy and Blackall (1987). The experimental program was carried out at Cape Hatt, near the northern tip of Baffin Island, in Canada’s eastern Arctic. This location is a typical eastern arctic ecosystem; physical, geochemical and biological settings are detailed elsewhere (Buckley eral., 1987; Cretneyetal., 1987a,b,c; Snow et al., 1987). The program continued for four years (1980-83). Baseline data were collected in the first year and two experimental oil releases each of approximately 15 m3 of weathered (8% by volume) Lagomedio crude oil occurred in the second year. The f i t release was directly onto the water surface of a sheltered bay (Bay 1 1; see Fig. l), and the second release, one week later, was of oil premixed with dispersant (10: 1) into the water column of another bay (Bay 9; see Fig. 1) at depths from 3

to 10 m (Dickins et al., 1987). This paper describes the fate of both the untreated and the dispersed oil in subtidal benthic marine animals.

The fate of the oil was also monitored in the water column (Humphrey et al., 1987) and in the sediments (Boehm et al., 1987). The effects of oil releases on the microbial communities (Bunch, 1987) and on the macrobenthos (Cross et al., 1987a,b; Cross and Thomson, 1987) are also described elsewhere.

The benthic chemistry segment of the BIOS program examined the hydrocarbon content of a number of selected inverte- brate species chosen from the local benthic community as sentinel (Phillips, 1980) organisms, but also found elsewhere in the Canadian Arctic (Thomson, 1982; Thomson et al., 1987). The animals were analyzed for total oil content, and the oil from selected animals or composites was subjected to detailed compositional analysis to study its fate.

Many previous studies have examined the effects of oil on benthic invertebrates (e.g., Atlas et al., 1978; Gilfillan and Vandermeulen, 1978;,Percy, 1976). Various lethal and sublethal effects on arctic biota have been observed (see, for example, Wells and Percy, 1985; Rice et al., 1984; Hutcheson and Harris, 1982), and it has been postulated (Elmgren et al., 1983) that more than five years may be required for full recovery of communities exposed to oil even in temperate areas.

Some studies have compared the effects of dispersed and untreated oil on the benthos. Tjessem et al. (1984) studied the fate of dispersed crude oil in enclosed sea water containers (mesocosms) off the coast of Norway. They found high concen-

‘Seakem Oceanography Ltd., 2045 Mills Road, Sidney, British Columbia, Canada V8L 3S1 ’Battelle Ocean Sciences, 397 Washington Street, h b u r y , Massachusetts 02332, U.S.A. 3Nati0nal Wildlife Research Centre, Canadian Wildlife Service, Environment Canada, Ottawa, Ontario, Canada KIA OE7 @The Arctic Institute of North America

150

FIG. 1. Location of experimental bays at Cape Hatt, N.W.T. Bay 9 is the site of the dispersed oil release. Bay 1 1 is the. site of the surface oil release.

trations of hydrocarbons (including the toxic polar and high molecular weight components) in the entire water column, but the biota were not monitored for hydrocarbon uptake. Farke et al. (1985) used mesocosm experiments to study the effects of dispersed oil on intertidal organisms. Chemical dispersion of the oil resulted in more retention of the lower molecular weight

B . HUMPHREY et al.

aromatic components and generally higher oil concentrations in the mesocosm systems. The concentration of hydrocarbons was not monitored in the biota, but sublethal effects were observed. Crothers (1983) reported on field observations of the effects of experimentally dispersed oil on the fauna and flora of rocky shores. Dispersed oil was found to have a larger impact (as measured by species survival and recolonization rates) than untreated oil. However, recovery was rapid in both cases, although slightly slower in winter than in summer.

Most studies of hydrocarbon accumulation and release by biota have been conducted in the laboratory; many of these studies were reviewed by Neff and Anderson (1981). Few have examined the concentrations and compositional changes (Gor- don et al . , 1978) of petroleum hydrocarbons in animals exposed to oil. The 1981 dispersant effectiveness tests in Searsport, Maine, did monitor the hydrocarbon concentrations and compositions in two filter-feeding species, Mya arenaria and Mytilus edulis. Only those animals exposed to undispersed oil took up measurable amounts of oil, and hydrocarbon depuration was rapid (approximately one month) and complete.

The interdisciplinary BIOS Project provided an opportunity to examine all aspects of the fate of oil in benthic invertebrates over a long period of time. The results of the field studies are reported in this paper. Laboratory studies conducted in conjunc- tion with the BIOS field experiments have also studied the uptake and depuration of oil dispersed in the water column by arctic invertebrates (Mageau et al . , 1987) and are reported elsewhere in this journal.

METHODS

Sentinel animals were chosen from the Macoma community, a widespread and common feature of the High Arctic nearshore. This community includes the bivalve species selected for this experiment: Macoma calcarea (CAL), Mya fruncafa (TRU), Astarte borealis (BOR) and Serripes groenlandicus (GRO). In addition an urchin, Strongylocentrotus droebachiensis (DRO) , a common grazer, was selected. These animals include filter feeders (BOR, TRU and GRO) and deposit feeders (CAL and DRO). Differences in oil uptake between filter and deposit feeders have been observed in other locations by Roesijadi et al. (1978), where the oil contamination was in the sediments rather than the water column.

The sampling strategy was determined by the baseline biological study (Cross etal . , 1987a,b; Cross and Thomson, 1987) and is discussed in detail by Cretney et al. (1987~). Biota samples were collected for hydrocarbon analysis from specific tissue plots (see Fig. 2) at two water depth strata in each bay. Sediment samples were collected from the same plots for hydrocarbon analysis by methods similar to those used for the tissue hydrocarbon analyses. There were five tissue plots per depth stratum, situated adjacent to the biological study areas (benthic transects; see Fig. 2). The monitoring program included four bays (Bays 7, 9,lOandll;seeFig. l)andfivesamplingperiods(1980,1981a, 1981b, 1982 and 1983). Specifically, sediment and biota samples from all bays were collected and analyzed in 1980 and 198 1 to determine baseline conditions (Cretney et al., 1987a,c). Samples were also collected from Bay 11 (the site of the surface release on 19 August 1981) one day after that release (1981a). Samples were collected from the other bays one or two days after the dispersed oil release (also 1981a) that took place on 27 August 1981 in Bay 9. Bay 10 was intended to be used as a

FATE OF OIL IN BENTHIC BIOTA

I 1 a

uuuuu 1 a 4 0

RG. 2. Biota sampling locations in experimental bays.

control but was contaminated by the spill in Bay 9; Bay 7 was therefore used as a control from 1981 on. Sediment and biota in all bays were resampled two weeks after the dispersed oil release (1981b) and again in 1982 and 1983. Not all designated samples were collected or analyzed in later sampling periods. For example, samples were not collected from any of the 3 m strata tissue plots in 1982 and 1983 or from Bay 10 in 1983 to focus the analytical effort. By the end of the project, a set of results for five species from four bays at 7 m depth and five sampling periods (four periods for Bay 10) was available for detailed statistical analysis.

Animals were collected by divers. Most animals were collected by an airlift method (Snow et al., 1987), except for urchins and some S . groenlandicus, which were hand-picked. A minimum of ten animals of each species was taken from each plot. After collection, the animals were wrapped in aluminum foil, bagged and frozen until analysis.

Details of the analytical procedures are given in the BIOS working reports (Boehm, 1981, 1982, 1983; Boehm et al., 1984). Hydrocarbons were extracted from the tissue samples and the oil contents of the extracts determined by ultraviolet/ fluorescence (UV/F) spectroscopy. Extract composites were also examined by gas chromatography with flame ionization (GC/FID) and mass spectrometric (GUMS) detection to determine hydrocarbon compositions.

The extraction scheme is based on that of Warner (1976). Animals were thawed just prior to analysis. Tissue was removed from the shell or exoskeleton with solvent-cleaned utensils and homogenized to produce a composite sample from the whole tissues of at least ten animals. A subsample was used for wet weighvdry weight determination. Internal standards were added to the remainder, which was digested overnight with 10 ml of 5N KOH. The digest was extracted with hexane, which was then dried and reduced in volume to about 1 ml by rotary evaporation. Prior to UV/F analysis, the extracts were eluted through an alumina column with 9:l hexane:dichloromethane to remove interfering polar and biogenic compounds. The eluate volume was reduced to about 2.5 ml.

The UV/F analysis is based on methods developed by Lloyd (1971a,b,c)andlaterusedbyWakeham(1977)andBoehmetal. (1 982). The method relies on the separation of emission peaks of multi-ring aromatics when the emission and excitation wave- lengths are scanned simultaneously with a set wavelength separation. When scanned with a separation of 25 nm, Lagomedio crude oil shows a peak at 325 nm excitation wavelength and 350 nm emission wavelength. This peak was used as the identifier

151

for the experimental oil. Oil concentrations were determined by comparing sample extract peak heights to standard peak heights from a curve derived from Lagomedio crude oil. Results are reported as Lagomedio equivalents.

Data from the UV/F analyses were evaluated statistically. Data were log transformed and all statistical analyses carried out on log data. Log transformation provided a data set with quite homogeneous variances, thus permitting statistical analysis of the results. To determine equivalency of means from two sets of five analyses, Student's t for a two-group comparison was determined and compared to t from a table, based on 95% probability. An F test, again at 95% probability, was performed when more than two sets of sample means appeared to be equivalent.

Extract composites for UV/F analysis were subsequently analyzed by capillary gas chromatography (Cretney et al . , 1987~). Extracts were fractionated by elution through a column packed with 11 g 100% activated silica gel, 1 g 5% deactivated alumina and 1 g copper. The sample was placed on the column, eluted first with hexane to remove the non-polar aliphatic compounds (Fl), followed by 1: 1 dich1oromethane:hexane to remove the polar aromatic components (F2).

The aliphatic F1 fraction was analyzed by capillary GC/FID. The aromatic F2 fraction was analyzed by GUMS using the selected ion monitoring technique (SIM) to determine concentrations of selected aromatic hydrocarbons. Procedural details are given in the BIOS working reports (Boehm, 1982, 1983; Boehm et al . , 1984).

A set of weathering indexes determined for each sample analyzed by GC/FID or GUMS was used to aid in interpretation of the results.

RESULTS

The results of the UV/F analyses of the tissue samples from Bays 11, 10, 9 and 7 are reported in Tables 1-4. Results are presented graphically in Figure 3 and represent baseline sampling, twopost-release samplings in 1981 and samplings in 1982 and 1983 (except for Bay 10). An important point regarding sampling periods is that in Bay 11, the 1981a period occurred after the surface release in that bay, but before the dispersed release in Bay 9. For all other bays, the 198 la sampling period occurred just after the dispersed oil release. The 198 lb sampling period occurred in all bays two weeks after the dispersed oil release and three weeks after the surface release.

The levels of exposure to dispersed oil experienced by the animals in Bays 7, 9 and 10 were calculated from measured water column oil concentrations (Humphrey et al., 1987). These results are presented in Table 5 .

Comparisons were made between oil contents of airlifted and hand-picked S . groenlandicus samples and between samples from the two depth strata (Boehm, 1982). No differences were observed between the two sampling methods, but animals from the 3 m stratum usually contained slightly more oil than those from the 7 m stratum. The 3 m stratum was discarded after 1981 to focus the analytical effort, as animals were less abundant at that depth.

Baseline data indicate considerable inter-species and inter- bay variability, although all baseline data are low compared to post-release levels. Some differences that stand out are the relatively high baseline oil equivalent levels in A. borealis and M. culcarea from Bay 7 and the generally high oil equivalent levels in S. droebachiensis from all bays.

152

TABLE 1 . UV/F analysis of oil content of Bay 1 1 tissues

Log transformed data Geometric Number Standard mean

Animal Bay Year of plots Mean deviation (pg.g")

BOR BOR BOR BOR BOR CAL CAL CAL CAL CAL TRU TRU TRU TRU TRU GRO GRO GRO GRO GRO DRO DRO DRO DRO DRO

11 Baseline 11 1981A 11 1981B 11 1982 11 1983 11 Baseline 11 1981A 11 1981B 11 1982 11 1983 11 Baseline 11 1981A 11 1981B 11 1982 11 1983

11 1981A 11 Baseline

11 1981B 11 1982 11 1983 11 Baseline 11 1981A 11 1981B 11 1982 11 1983

5 5 4 5 5 4 5 4 5 5 5 5 5 5 5 1 4 3 4 5

5 5 5 5 5

-0.38 0.43 2.15 1.57 1.18 0.33 1.39 2.39 1.78 1.80

-0.37 0.28 1.97 0.12 0.58

0.73 2.59 1.11 1.04 1.10 1.89 2.63 1.66 2.01

.29 0

.08 3

.28 140

.04 37

.45 15

.50 2

.I9 24

.32 250

.15 60

.16 64

.08 0

.17 2

. 0 9 93

.I3 1

.42 4 11

.60 5

.19 390

.24 13

.I9 11

.27 13

.70 78

.47 430

.17 46

.26 l o o ~~

1981A: aftersurfacerelease,beforedispersedrelease,Bay 11 only 1981-08-21. 1981B: 1981-09-08. BOR: A . borealis. CAL M. calcarea. TRU: M. truncata. GRO: S. groenlandicus. DRO: S. droebachiensis.

TABLE 2. UV/F analysis of oil content of Bay 10 tissues


Animal Bay Year of plots Mean deviation (pg.g-') BOR 10 Baseline 5 -0.38 .16 BOR 10 1981A

0 4 2.56 .03

BOR 10 1981B 360

5 2.49 .14 BOR 10 1982

310 5 1.40 .08 25

CAL 10 Baseline 5 0.29 .23 CAL 10 1981A 5

2 2.61

CAL 10 1981B 4 .18 410

2.72 .09 CAL 10 1982

520 5 1.14 . 0 9 14

TRU 10 Baseline 5 -0.25 .IO TRU 10 1981A 5

1

TRU 10 1981B 2.44 .14

5 280

TRU 10 1982 2.20 .I3 160

5 -0.02 .I2 1 GRO 10 Baseline 5 0.10 .30 GRO 10 1981A

1 5 2.51 .08 320

GRO 10 1981B 4 GRO 10 1982

2.15 .06 140 5 0.47 .07 3

DRO 10 Baseline 5 1.28 .34 DRO 10 1981A

19 5 1.95 . l l

DRO 10 1981B 89

5 DRO 10 1982

2.03 .I3 110 5 1.31 .10 20

1981A: 2 days after dispersed release, 1981-08-29.

BOR: A . borealis.

TRU: M . rruncutu. CAL: M. calcarea.

GRO: S. groenlandicus. DRO: S. droebachiensis.

1981B: 1981-09-11.

B. HUMPHREY et al.

TABLE 3. UV/F analysis of oil content of Bay 9 tissues


Animal Bay Year of plots Mean deviation (pg.g") BOR BOR BOR BOR BOR CAL CAL CAL CAL CAL TRU TRU TRU TRU TRU GRO GRO GRO GRO GRO DRO DRO DRO DRO

9 Baseline 9 1981A 9 1981B 9 1982 9 1983 9 Baseline 9 1981A 9 1981B 9 1982 9 1983 9 Baseline 9 1981A 9 1981B 9 1982 9 1983 9 Baseline 9 1981A 9 1981B 9 1982 9 1983 9 Baseline 9 1981A 9 1981B 9 1982 9 1983

4 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5

-0.10 2.66 2.23 1.28 0.84

-0.15 1.87 2.92 1.40 1.10

-0.47 2.08 2.06

-0.09 0.47

-0.33 2.40 1.98 0.71 0.01 1.20 1.65 2.33 1.67

.16 1

.19 460

.23 170

.26 19

.10 I

.22 1

.25 75

. l l 840

.13 25

.27 13

.I5 0

.30 120

.08 110

.20 1

.25 3

.45 0

.14 250

.17 96

.10 5

.24 1

.15 16

.11 45

.20 220

.22 46

.25 150 DRO 2.18

1981A: 1981-08-28. 1981B: 1981-09-10. BOR: A . borealis.

TRU: M. truncata. CAL: M. calcarea.

GRO: S. groenlandicus. DRO: S. droebachiensis.

If Bay 11 (surface oil release) data are disregarded, two predominant patterns emerge from the results. For the filter feeders A . borealis and S. groenlandicus, oil concentrations increased immediately after the dispersed oil release and began to decrease by the next sampling, continuing to decrease the following years. The filter feeder M. rruncata also follows this pattern except that an increase is observed in 1983. For the deposit feeders M. calcarea and S. droebachiensis, the increase occurred more gradually over the two 1981 sampling periods, decreased in 1982 and increased again in 1983. An exception to this pattern is seen for M. calcarea in Bay 9, in which the increase in 1983 is not observed.

The data plotted in Figure 3 can be used to make an inter-bay comparison of the uptake/depuration responses of the species studied. The filter feeder response was more dramatic in Bay 7 animals than in those from Bays 9 and 10. Bay 7 filter feeders showed rapid uptake and depuration of the oil, while those in Bays 9 and 10 rapidly took up oil but depurated it more gradually. The deposit feeder response was similar among Bay 9 and 10 animals, while those in Bay 7 took up less oil and depurated it to lower levels.

The data for Bay 11 (Table 1; Fig. 3a) indicate that a small increase in oil concentration occurred in all animals after the surface oil release in that bay (1981a), but that increase was minor compared to the increases observed after the dispersed oil release in Bay 9 (1981b). Later samplings (1982,1983) indicate that the oil concentrations remain generally higher in Bay 11 animals than in those in other bays.


TABLE 4. UVlF analysis of oil content of Bay 7 tissues


Animal Bay Year of plots Mean deviation (bg.g")

BOR BOR BOR BOR BOR CAL CAL CAL CAL CAL TRU TRU TRU TRU TRU GRO GRO GRO GRO GRO GRO DRO DRO DRO DRO DRO

7 Baseline 7 1981A 7 1981B 7 1982 7 1983 7 Baseline 7 1981A 7 1981B 7 1982 7 1983 7 Baseline 7 1981A 7 1981B 7 1982 7 1983 7 Baseline 7 1981A 7 1981B 7 1982 7 1983 7 1983 7 Baseline 7 1981A 7 1981B 7 1982 7 1983

4 0.31 5 1.70 4 1.75 5 0.83 5 0.22 5 0.02 5 1.91 5 1.93 5 0.28 5 0.72 5 -0.48 5 2.06 5 1.67 5 -0.38 5 0.04 3 0.04 4 2.71 3 1.88 5 0.33 5 0.32 4 0.06 5 1.09 5 1.66 5 1.62 5 0.78 5 1 . 0 9

.32 2

.52 50

.26 56

.27 7

.44 2

.06 1

. l l 82

.27 85

.07 2

.4 1 5

.13 0

.21 110

.14 47

.13 0

.15 1

.07 1

.10 520

.28 75

.16 2

.63 2

.29 1

.12 12

.12 46

.13 42

.24 6 -28 12

1981A: 1981-09-01. 1981B: 1981-09-11. BOR: A . borealis.

TRU: M. truncata. CAL: M. calcarea.

GRO: S. groenlandicus. DRO: S . droebachiensis.

Gas chromatographic analysis of the F1 alkane and F2 aromatic fractions of the tissue extracts provided information on their hydrocarbon composition. The presence of petrogenic material could be detected, and its degree of weathering and biodegradation was estimated through a qualitative examination of the chromatograms and evaluation of the weathering indexes described in Table 6. Unoiled tissues contain significant quanti- ties of biogenic hydrocarbons originating from planktonic material (nCI7 and pristane) and terrigenous plant materials (odd carbon chain normal alkanes C25 through C33). The presence of oil in the F1 aliphatic fraction is indicated by phytane and a series of odd and even carbon number n-alkanes. The presence of oil in the F2 aromatic fraction is indicated by the presence of alkylated naphthalenes, phenanthrenes and dibenzothiophenes. Loss of low molecular weight aliphatic components (both normal and branched alkanes) followed by loss of low molecular weight aromatics (the naphthalene compound series) was taken as indication of weathering. Two ratios of normal alkanes to isoprenoid alkanes (n-alkaneslisoprenoids and nC18/phytane; see Table 6) are used to estimate the extent of biodegradation of the oil. Aromatic fraction degradation was indicated by the dominance of alkylated phenanthrenes and dibenzothiophenes in the aromatic fraction. The presence of unresolved complex mixture (UCM) in the F1 fraction was used as an indicator of degraded oil.

Results of the gas chromatographic analyses of tissue extracts fromBay11,10,9and7animalsaresummarizedinTables7-10.

153

Note that a somewhat subjective interpretation of the chromatographic patterns is also offered in these tables. Complete sets of chromatograms (GC/FID of the F1 aliphatic and F2 aromatic fractions, GUMS of the F2 fractions) have been reported in the BIOS workingreports(Boehm, l981,1982,1983;BoehmetaZ., 1984; Engelhardt and Norstrom, 1982). Representative chromatograms and aromatic distributions are shown in Figure 4 and discussed below.

The results of the GC/FID analyses of the F1 aliphatic fractions of the tissues show general trends with some special cases. Immediately after the surface oil release in Bay 1 1, but before the dispersed oil release, the tissue extract chromatograms from Bay 11 biota did not indicate the presence of oil. Immedi- ately after the dispersed oil release, however, chromatograms from most species from all bays indicate the presence of slightly weathered oil, similar to the released oil. Figure 4a is a typical chromatogram of the F1 fraction of this type of sample. The features of note are the resolvable n-alkanes from C 12 to C30 and several isoprenoids. Special cases are A . borealis samples, which contain a more biodegraded oil than other species (as indicated by the near absence of n-alkanes less than C22 and an alkane/isoprenoid ratio of 0.1; see Tables 7-10), and S. droebachiensis, which do not appear to contain oil (as indicated by the absence of phytane).

By the second 1981 sampling period, relatively degraded oil was common in most tissue samples. A typical chromatogram of the F1 fraction of these samples is shown in Figure 4b. Note the loss of resolved n-alkanes along with the persistence of several isoprenoids and a significant UCM. These features are indica- tive of biodegradation, most likely occurring in vivo, as there is no evidence of such degradation occurring to any significant extent within this period in either the water or sediment (Boehm, 1982). A . borealis samples again contained a more biodegraded oil than the other species, and Bay 11 tissues contained the least weathered oil. S. droebachiensis samples again indicated low oil content.

Samples collected and analyzed in 1982 are all very similar to each other. A typical chromatogram of the F1 aliphatic fraction is shown in Figure 4c. A significant UCM and a large amount of pristane indicate the presence of heavily weathered oil. A new feature is present in many of the chromatograms: a suite of n-alkanes from C23 to C33 with a significant odd-even predomi- nance. This feature is typical of terrigenous wax material, usually of plant origin. The decreased amount of oil in the 1982 tissues compared to the 1981 tissues (see data in Fig. 3) could account for the relative prominence of the terrigenous material in Figures 4c and 4d.

The M. truncatu and the S. groenlandicus samples also contain some fresh oil, as indicated by the presence of low molecular weight alkanes (Cl4-CzO range). The other filter feeder, A . borealis, did not show this low molecular weight material, but it could have degraded it more rapidly.

By 1983, the chromatograms of most samples display very few features that can be associated with the original oil. Figure 4d is a typical 1983 chromatogram of the F1 aliphatic fraction, with no identifiable C10-C22 n-alkanes, significant amounts of pristane (a biogenic hydrocarbon) and a suite of terrigenous components in the C23- C33 range. Bay 11 tissues, however, are an exception, as their chromatograms show significant petrogenic hydrocarbons even in 1983.

In general, GC/FID analyses of the F1 aliphatic fractions indicate that oil was taken up by the animals in all bays after the

B. HUMPHREY e? al.

- BASELINE

- 1981 a

- 1981 b

- 1982

- !983

FIG. 3. Concentrations of oil in tissues by UV/F spectroscopy: a. Bay 11; b. Bay 10; c. Bay 9; d. Bay 7. BOR, A . borealis; CAL, M. calcarea; TRU, M. truncata; GRO, S. groenlandicus; DRO, S. droebachiensis. The data plotted are. the geometric means of the results for one composite sample from each tissue plot. Up to five tissue plots were sampled in each bay (see Fig. 2 and Tables 1-4 for details). The indicated standard deviation therefore includes both sampling and analytical variability.

dispersed oil release. Oil began to be depurated and degraded out in the results: biodegradation of aliphatics appears to occur immediately and continued to do so until no recognizable oil in vivo in all species, but at a faster rate in A . borealis than in the components remained after two years. After one year, some other species, and S. droebachiensis does not appear to retain fresh oil appeared in the chromatograms along with degraded any oil. oil, but it was not in evidence after two years. Two features stand G C M S analyses of the tissue F2 aromatic fractions give


TABLE 5 . Exposure levels

Maximum* S. groenlandicus water column Exposure* body burden concentration mg.l".h (IJ.g.g")

(mg.1") (at 7 m) 1981A 1981B Bay 9 160 300 250 96 Bay 10 1.2 30 320 140 Bay 7 0.1 1 520 75

*Humphrey er al . , 1987.

TABLE 6. Explanation of hydrocarbon weathering indexes

1. Alkane/Isoprenoid Ratio (Biodegradation) AMIso = nCl4 + nCl5 + nC16 + nCI7 + nCl8

FARN + TM 13 + NOR + PRIS + PHYT This ratio approaches 0 as the n-alkanes are preferentially depleted.

2. nC,,/Phytane Ratio This ratio approaches 0 as nCls is preferentially depleted during biodegradation. This is a specific case of the AlWIso ratio.

3. aPristane/Phytane Ratio Pristane occurs commonly in biota and in recent sediments as a degradation product of the phytol side chain of plant pigment chlorophyll, whereas phytane is not formed and is not commonly found in recent sediments; consequently, non-petroleum-derived hydrocarbons generally give rise to a high pristane/phytane ratio. The pristane/ phytane ratio has been used as an indicator of the presence or absence of petroleum. Although a high pristane/phytane ratio is generally a reliable indicator of the absence of petroleum, the converse is not necessarily true, that is, low values are less reliable indicators of the presence of petroleum hydrocarbons. Typical background values for this ratio are -5 , as reported by Boehm (1981).

4. Saturated Hydrocarbon Weathering Ratio (SHWR) sHWR = sum of n-alkanes from nClz to nCZ5

sum of n-alkanes from nCI7 to nCz5 The S H W R approaches 1 .O as low-boiling saturated hydrocarbons (nC12-ncI.l) are lost by evaporation.

5 . Carbon Preference Index (CPI) c p ~ = 2(nCz7 nCz9)

nCz6 + 2nCZ8 + nC3,, CPI = 1.0 for petroleum

CPI ranges from 3 to 6 for terrigenous waxes, reflecting the formation mechanism for long chain hydrocarbons.

6. Aromatic Weathering Ratio Alkyl benzenes + naphthalenes + fluorenes

Total phenanthrenes + dibenzothiophenes AWR = phenanthrenes + dihenzothiophenes

The AWR approaches 1 .O as low-boiling aromatics are lost by evaporation and/or dissolution.

similar generalized results. Immediately after the surface oil release in Bay 11, but before the dispersed oil release, tissue samples from Bay 11 species did not contain any aromatic oil compounds. Immediately after the dispersed oil release in Bay 9, biota from both Bays 9 and 10 contained fresh oil, as indicated by the abundance of naphthalene compounds (see Tables 7-10). A typical distribution of the aromatic component of these tissues is shown in Fig. 5a. Again the S. droebachiensis do not appear to contain significant concentrations of oil. Samples collected two weeks later in all bays indicate that oil degradation is proceed-

155

ing. The aromatic distribution outlined in Fig. 5b shows the near absence of naphthalenes and a decrease in the concentration of phenanthrenes relative to the dibenzothiophenes. It is notable that A . borealis does not differ from other biota in the F2 fraction, although the A . borealis F1 fraction shows considera- bly more degradation at this sampling period.

In 1982, tissue F2 fractions are more typical of fresh oil than those from the end of 1981 (as indicated by the presence of the lower molecular weight naphthalenes; see Tables 7-10). In particular for M. rruncata, S. groenlandicus and S. droebachiensis, naphthalenes dominate the aromatic distributions. There is an apparent contradiction in the S. droebachiensis results in that the animals appear to have taken up or retained only the aromatic components of the oil: the aliphatic fraction chromatograms did not show significant petrogenic hydrocarbon content. By 1983, no recognizable components from the original oil remain in most tissue samples except those from Bay 11.

Whole animal tissues were analyzed throughout this study. For practical reasons no attempt was made to estimate the effect of varying proportions of gut and tissue and of different tissue types in the samples. However, in 1981 both whole tissues and specific tissue parts of a large collection of S. groenlandicus from Bay 10 were analyzed to verify that the petrogenic hydrocarbons were contained in the animal tissue and not only in the gut. Little difference was observed between F1 fractions from the guts of the animals as compared to the rest of the tissue, but significant differences were observed when comparing the F2 fractions. Muscle tissue contained generally higher levels of lower molecular weight aromatics (the naphthalenes and alkylbenzenes), and generally lower levels of the higher molecular weight aromatics than the guts. However, these low molecular weight components are easily lost during the sample workup, and it is therefore difficult to make conclusions based on such differences when observed in only a small number of samples. Other sources of uncertainty are the influence of changes in species population on body burden data and the effects of differences in age structure, condition and life cycle stage of the organisms sampled from year to year. The magnitudes of these effects on the data are unknown.

DISCUSSION

Certain patterns appear from statistical analysis of the biota body burden data (Tables 1-4). Most obvious is the difference in initial hydrocarbon uptake between filter feeders and deposit feeders. Filter feeders picked up oil from the water column immediately after the dispersed oil release, with organisms from all bays giving similar results. Deposit feeders picked up hydrocarbon more slowly than filter feeders but had similar oil content by two weeks after the dispersed oil release. The pattern continues, with filter feeders and deposit feeders depurating oil over the first winter season, and with deposit feeders appearing to take up more oil over the following year, while filter feeders generally continue to depurate oil. Typically, the oil content of filter feeders increased by lo00 times in 1981 and was followed by reductions to Y~O-YIGU of the maximum body burden of 1982 and another 1/10 reduction to near baseline levels by 1983. Similar differences in oil uptake rates between filter feeders and deposit feeders have been observed in laboratory simulations of the BIOS field experiments (Mageau et al., 1987).

Baseline results of the UV/F oil analysis are variable among

156 B . HUMPHREY et al.

TABLE 7. Gas chromatographic results from Bay 1 1 tissues

Animal Year F1 (Aliphatic)

BOR 1981A No oil 1981B Moderate biodegradation up to nCzo; high UCM 1982 Moderate biodegradation; high UCM 1983 Low oil; moderate biodegradation up to nCzo; double UCM Low alkylated Ps and alkylated DBTs only

~ ~~

F2 (Aromatic)

No oil No Ns; alkylated Ps and alkylated DBTs persist No Ns; alkylated Ps and alkylated DBTs persist

CAL 1981A No oil: CPI = 1.9 Low Ns and Ps; no DBTs 1981B Oil: CPI = 1; little biodegradation No Ns; high Ps and DBTs 1982 High oil; moderate biodegradation No Ns; high Ps and DBTs 1983 High oil; moderate biodegradation up to C,; Low oil; alkylated Ps only

high isoprenoids and UCM

1981B Low oil: pridphyt = 10 1982 Biodegraded: C18/phyt = 0.1 1983 More oil; biodegradation up to nCzo; high UCM High alkylated P; no DBTs

and phytane

1981B 1982

Little biodegradation up to Cz2 Little degradation: no Ns, high alkylated P and alkylated DBTs

1983 Low new n-alkanes Clo-Czz; UCM Ns dominate; little DBTs and Ps More oil; biodegraded up to Czo; high UCM Low alkylated Ns and P, no DBTs

1981B 1982

Little biodegradation: loss of n-alkanes Little weathering: high alkylated P, alkylated DBT and UCM

1983 New n-alkanes ClO-Cz2; high UCM and isoprenoids Moderate oil; Ps and DBTs dominate Low oil: pridphyt = 14; some new oil: Low oil; alkylated Ns dominate c18/phyt = 1.0; high UCM

DRO 1981A No oil: prislphyt = 47 No oil Low oil: some Ns, Ps and DBTs Ns and Ps dominate

GRO 1981A No oil No oil

TRU 1981A No oil No oil

BOR = Astarre borealis. P = phenanthrene. CAL = Macoma calcarea. Ps = phenanthrene compound series. DRO = Strongylocentrotus droebachiensis. DBT = dibenzothiophene. GRO = Serripes groenlandicus. DBTs = dibenzothiophene compound series. TRU = Mya truncata. UCM = unresolved complex material. N = naphthalene. C18/phyt = nCI8/phytane ratio (see Table 6). Ns = naphthalene compound series. pridphyt = pristane/phytane ratio (see Table 6).

CPI = carbon preference index (see Table 6).

TABLE 8. Gas chromatographic results from Bay 10 tissues

Animal Year F1 (Aliuhatic) F2 (Aromatic)

BOR 1981A 1981B 1982 1983

CAL 1981A 1981B 1982 1983

DRO 1981A 1981B 1982 1983

GRO 1981A 1981B 1982 1983 1981A 1981B

TRU

1982 1983

Moderate biodegradation: &is0 = 1.3 High biodegradation up to nCzo; &is0 = 0.1 Very low oil N.A. High oil; CPI = 1 Little biodegradation; C,$phyt = 0.7 Less oil, moderate degradation N.A. No oil: pridphyt = 42 Low oil: pridphyt = 18 Low oil N.A. Fresh oil Little biodegradation up to nCzz; double UCM Low new n-alkanes Clo-Cz2; some UCM N.A. Fresh oil Loss of n-alkanes; isoprenoids and UCM persist

Less oil; new n-alkanes C10-C2z; high UCM N.A.

High Ns, Ps and DBTs High oil; loss of Ns only Ps and DBTs persist N.A. N.A. N.A. No Ns; alkylated P and alkylated DBT dominate N.A. No oil Low oil: low Ns, Ps and DBTs Low oil; Ps dominate N.A. Fresh oil: high Ns, Ps, DBTs Ps, DBTs and alkylated N persist Alkylated N and alkylated P persist; low DBTs N.A. Fresh oil: high Ns, Ps, DBTs Less oil; loss of Ns, P, DBTs; alkylated P, alkylated DBT and UCM persist Less oil; new Ns dominate N.A.

BOR CAL DRO GRO TRU N.A. N Ns

~~~~~

= Astarre borealis. = Macoma calcarea. = Strongylocentrotus droebachiensis. = Serripes groenlandicus. = Mya truncata. = not analyzed. = naphthalene. = naphthalene compound series.

~~ ~

P Ps DBT DBTs UCM c18/phyt PridPhyt &is0 CPI

= phenanthrene. = phenanthrene compound series. = dibenzothiophene. = dibenzothiophene compound series. = unresolved complex material. = nCl$phytane ratio (see Table 6). = pristane/phytane ratio (see Table 6). = n-alkandisoprenoid ratio (see Table 6). = carbon preference index (see Table 6).



157

Animal Year F1 (Aliphatic) F2 (Aromatic)

BOR 1981A Moderate weathering up to C14; W i s o = 2.0 High Ns, Ps and DBTs 1981B High biodegradation up to C22; W i s o = 0.2 Less oil; loss of N; Ps and DBTs persist 1982 Low oil Low alkylated P and alkylated DBT 1983 Low oil; biodegradation up to Cz0; double UCM Low alkylated P only

1981B More oil: CPI = 1; little biodegradation; More oil; no compositional changes

1982 Moderate degradation No Ns; alkylated P and alkylated DBT dominate 1983 Low oil; low phytane and UCM P dominant

1981B Low oil: pris/phyt = 21 High Ps and DBTs 1982 More oil: phytane, n-alkanes, moderate degradation: Low DBTs; some Ps

1983 Low oil; high UCM only No oil GRO 1981A Fresh oil: n-alkanes down to Clo Fresh oil: high Ns, P, DBTs

1981B Little biodegradation up to nCZ2; double UCM No Ns; Ps and DBTs persist 1982 Less oil; new n-alkanes ClO-Cz2; small UCM Little degradation: N dominate 1983 No oil No oil

1981B Loss of n-alkanes; isoprenoids and UCM persist Loss of Ns, P, DBT; alkylated P, alkylated DBT and UCM persist 1982 Less oil; new n-alkanes ClO-Cz2; high UCM; Less oil; new Ns dominate

1983 No oil: oris/uhvt = 50 No oil

CAL 1981A Low oil: CPI = 1.3; C18/phyt = 1.7 High Ns, Ps and DBTs

Cls/phyt = 0.8

DRO 1981A No oil: pris/phyt = 121 Some Ns, Ps and DBTs

some UCM

TRU 1981A Fresh oil: n-alkanes down to Cl0 Fresh oil: high Ns, Ps, DBTs

C,s/phyt = 0.6

BOR = Astarte borealis. CAL = Macoma calcarea. DRO = Srrongylocenrrotus droebachiensis. DBT = dibenzothiophene. GRO = Serripes groenlandicus. TRU = Mya truncata. N = naphthalene. Ns = naphthalene compound series. P = phenanthrene.


Ps DBT DBT DBTs UCM CIdPhyt PridPhyt aWiso CPI

= phenanthrene compound series. = dibenzothiophene. = dibenzothiophene. = dibenzothiophene compound series. = unresolved complex material. = nCI8/phytane ratio (see Table 6) . = pristane/phytane ratio (see Table 6) . = n-alkane/isoprenoid ratio (see Table 6). = carbon preference index (see Table 6) .

Animal Year F1 (Aliphatic) F2 (Aromatic)

BOR 1981A High biodegradation up to nCzo; W i s o = 0.2 Little degradation: low Ns, moderate Ps, DBTs 1981B 1982

High biodegradation Little depuration; no N, moderate P, DBTs

1983 No oil No oil Low oil: biodegradation up to Cm; double UCM Alkyl N, alkyl P, and alkyl DBTs

1981B No new oil: CPI = 1.3; biodegradation, Cls/phyt = 0.4 Low oil; weathered: only alkyl P and alkyl DBTs 1982 No oil 1983 Low oil; low UCM and phytane Alkyl N and alkyl P only

1981B Low oil: pris/phyt = 54 1982 No oil 1983 Low oil; low UCM and phytane Low P only

1981B Less oil; little degradation 1982 New n-alkanes CIo-CzZ, low UCM 1983 No oil No oil

TRU 1981A Little biodegradation: low C18/phyt

CAL 1981A Low oil: CPI = 1.3; no degradation N.A.

Low Ps only

No oil No oil Low oil; Ns dominate

Little degradation: low Ns; high Ps and DBTs Less oil; little degradation Low N, no DBTs; Ps dominate

Low oil; moderate degradation: low Ns, low UCM Less oil; no Ns, less Ps, DBTs Less oil; new Ns dominate

DRO 1981A No oil: pridphyt = 97

GRO 1981A Moderate biodegradation, W i s o = 0.2

1981B Less oil; more biodegradation 1982 Less oil; new n-alkanes C10-C22; high UCM 1983 Low oil: low UCM and low ohvtane Low oil: onlv low alkvl N oresent

BOR = Astarte borealis. CAL = Macoma calcarea. DRO = Strongylocentrotus droebachiensis. GRO = Serripes groenlandicus. TRU = Mya truncata. N.A. = not analyzed. N = naphthalene. Ns = naphthalene compound series.

P Ps DBT DBTs UCM C I dPhyt PridPhyt Wiso CPI

= phenanthrene. = phenanthrene compound series. = dibenzothiophene. = dibenzothiophene compound series. = unresolved complex material. = nC18/phytane ratio (see Table 6) . = pristane/phytane ratio (see Table 6). = n-alkanelisoprenoid ratio (see Table 6) . = carbon preference index (see Table 6).

158 B . HUMPHREY et al.

PRISTANE * ISOPRENOIOS

C I6

TERRIGENOUS MATERIAL

'RI STANE

L 1 C

L L ~ G . 4. Gas chromatogram (GC/FID) of the F1 aliphatic fraction of typical tissue extracts. a: Sample collected immediately after the dispersed oil release. b Sample collected two weeks after the dispersed oil release (1981b). c: Sample collected one year after the experimental oil releases (1982). d: Sample collected two years after the experimental oil releases (1983).

species. These hydrocarbon content differences have been examined by Cretney et a f . (1987c), who have related them in part to differences in feeding patterns. An interesting result was obtained for S. droebachiensis: they have a high oil equivalent content (UV/F method; see data in Tables 1-4) in baseline data, but this is not confirmed by GC methods, which show an absence of petrogenic hydrocarbons. No explanation for this was found.

The correspondence between UV/F oil analysis results and gas chromatographic compositional observations decreased with time. The correspondence was good at high hydrocarbon concentrations and with oil in a similar state of weathering as the original Lagomedio oil (Boehm, 1981,1982). By 1982, with oil concentrations decreasing, the GC/FID results for the F1 fractions underestimated oil concentrations in comparison to the UV/F results (Boehm, 1983; Boehm et a f . , 1984). This is not surprising, as GC methods are specific for relatively low molecular weight hydrocarbons, while the UV/F method is sensitive

l" co C I k c3 c4 (

1

I :3 L c4 co CI

FIG. 5. Distribution of aromatic hydrocarbons in tissues. a: Sample collected immediately after the dispersed oil release. b: Sample collected two weeks after the dispersed oil release. N, naphthalenes; P, phenanthrenes; DBT, dibenzothiophenes; C , indicates the number of carbon atoms in the alkyl side chain attached to the parent N, P or DBT compound.

to a wider range of molecular weights and is not specific to hydrocarbons but is sensitive to substituted polar compounds as well. Recent studies suggest that the UV/F spectrum is not significantly changed even after extensive weathering (Hum- phrey and Vandermeulen, 1986). It is likely that the UV/F method is more robust over time than the GC methods and that UV/F results from this study do indicate the presence of persis- tent Lagomedio oil, although the oil composition has changed. The UV/F determination may be sensitive to weathered oil components (e.g., oxidized aromatics), which are not determined in the GC analyses. This conclusion is supported by Farrington etaf. (1986), who suggest that non-agreement between UV/F and GC results is due to the presence of fluorescing hydrocarbons other than the aromatics normally determined by GC methods.

Any immediate changes in animal oil content caused by the surface oil release in Bay 11 are masked by the effects of the dispersed oil release in Bay 9. Only small increases in oil concentrations of Bay 11 organisms were measured in the first post-spill sampling (1981a; see Fig. 3a), which occurred before the dispersed oil spill in Bay 9. Gas chromatographic data for Bay 11 tissues (Table 7) do not indicate the presence of


petrogenic hydrocarbons except for biota from one sampling station (Engelhardt and Norstrom, 1982). However, by the second post-spill sampling period (two weeks after the dispersed oil spill in Bay 9), oil content of Bay 1 1 organisms was similar to that of organisms from all other bays for the same period. Results of later samplings, in particular those from 1983, indicate that oil is entering the benthic system two years after the experimental releases. While this material has the UV/F characteristics of the experimental oil, gas chromatography data do not indicate the presence of the lower molecular weight hydrocarbons that were present in 198 1.

Filter feeders residing in Bay 7 exhibit the greatest increases in oil concentration after the dispersed oil release. This is not expected from the level of exposure to dispersed oil experienced by these animals (see Table 5). The sea floor of Bay 9, the site of the dispersed oil release, was exposed to concentrations of oil well above 50 mg.1" for more than 12 h, with an integrated exposure of 300 mg.1-l.h (Humphrey et al., 1987). Bay 10 benthos were exposed to maximum concentrations and integrated exposures of 1/10 the levels of Bay 9, while Bay 7 animals were exposed to levels one order of magnitude lower again. Body burdens, as determined by UV/F, vary inversely to the hydrocarbon content of the water to which the animals were exposed. S. groenfandicus is the most obvious example. The data in Table 5 compare the hydrocarbon exposure levels (Humphrey et af., 1987) to the fist post-spill body burdens. While the differences in body burdens are not as extreme as the differences in exposure, they decrease with increased exposure. The difference in uptake may be related to some behavioural defense mechanism in Bay 9 and 10 animals in that they may have stopped pumping water for the period of intense exposure, while those in Bay 7 were not sufficiently stressed to invoke a similar reaction.

Results from later samplings do indicate differences in hydrocarbon uptake between different feeding types. The deposit feeders M. cafcarea and S. droebachiensis increase their oil contents after 1982. Results of the sediment analyses in the experimental area show that sediment oil content is also increas- ing (Boehm, 1987). The oil concentrations of Bay 11 and 9 sediments have increased from less than 1 mgekg" in both bays in 1980 and 1981 to 13 mg.kg" in Bay 11 and 8 mgekg" in Bay 9 in 1983. This source of hydrocarbon is available to the deposit feeding animals. An anomaly is the filter feeder M. truncata. For no apparent reason, the hydrocarbon content increased for M. truncata samples in all three of the sampled bays in 1983.

Gas chromatographic compositional analyses also show some general patterns. Most animals took up fresh oil immediately after the dispersed oil release, followed by loss of both aliphatic and aromatic hydrocarbons, as indicated by decreases in overall body burdens of these components. In vivo degradation of the n-alkane components of the oil was also indicated by the presence of a more biodegraded aliphatic fraction in the tissue samples than was present in either the water column or sediments at the same sampling period. There did not appear to be general differences in the composition of hydrocarbons taken up by filter and deposit feeders, although differences in depuration rates (Fig. 3) and characteristics (Tables 7-10) between species were evident. In other BIOS experiments, Mageau etaf. (1987) conducted tank simulations using this same oil and dispersant and also observed in vivo oil biodegradation in M. trruncatu and S. groenlandicus specimens.

The GC/FD data (Tables 7-10) suggest that A. borealis

159

degrades aliphatic components of oil very rapidly, although both UV/F and GUMS results indicate that the aromatic components do not degrade at a rate different from that in other animals. A greatly accelerated in vivo degradation is confi ied for A . borealis vs. other bivalves in that initial oil residues (1981a sampling) from Bay 7 A . borealis tissues contained no n-alkane components lighter than C20r while Bay 7 M. truncata and S. groenfandicus contained substantial n-alkane character in the CI4-CZOregion(Boehm, 1982). Theextentofthis biodegradation is greater in Bay 7 animals than in Bay 9 and 10 animals sampled at the same time, but this may be related to the higher overall levels of acquired petroleum in the Bay 9 and 10 organisms.

S. droebachiensis also provides some interesting detail. The GC/FID analyses indicate that little oil is taken up by the urchins, yet the UV/F and the GUMS indicate significant uptake. Mageau et al. (1987) also noted the near absence of petrogenic components in the F1 aliphatic fraction of S. droebachiensis extracts but observed only low concentrations of some petrogenic aromatics in the F2 fractions. It is possible that urchins degrade or depurate the aliphatic components so rapidly that they are not readily observed.

Most animals appear to retain aromatic components of the oil longer than aliphatic components. These observations are consistent with the results of Roesijadi et al. (1978) and are consistent with known patterns of biodegradation in which aliphatic components are most easily degraded by bacterial action.

The appearance of some low molecular weight aliphatics and aromatics in the 1982 tissue samples suggest that there may be a source of relatively fresh oil near the experimental sites. This effect was observed in all bays and may have been a conse- quence of oil leaching off the beach in Bay 11. Much of this stranded oil remained unweathered, probably due to its small surface area to volume ratio. The levels of fresh oil in the tissues were very low in all cases and were not observed again in 1983.

These results indicate that all biota accumulated petrogenic hydrocarbons following the 1981 experimental spills. The dispersed oil spill caused an immediate but short-lived infusion of oil to the water column and resulted in temporary accumulation of hydrocarbons by the benthos. These conclusions were also reached by Mageau et af. (1987) based on tank simulations of the BIOS dispersed oil spill. Similar patterns of oil accumulation and release by the various organisms studied were also ohserved in the field spill and in the tank simulations. Hydrocarbon levels in all species had returned to near baseline levels by 1983 except in Bay 11 (surface oil release), where oil concentrations were still slightly elevated. It is possible that oil stranded on the Bay 11 beach was still providing a source of petrogenic hydrocarbons to Bay 1 1.

A comparison may be made of the results of this work to those of a similar experiment carried out at Searsport, Maine (Page et al., 1983; Gilfillanetaf., 1985). Althoughnoexposureestimates were made for their untreated oil experiment, an estimate of the bottom exposure during the treated oil experiment (10% Corexit 9527 in Murban oil) was similar to the exposure observed in Bay 10 of the BIOS experiment. A significant difference between the experiments was that their method of spilling the oil mimicked a real spill situation more closely than did our procedure. The oilldispersant mixture was spilled on the water surface and dispersed into the water column using breaker boards; a conse- quence was that very little lower molecular weight material reached the bottom.

160 B. HUMPHREY et al.

Chemical monitoring of samples ofM. arenaria andM. edulis from well before the discharge until the following year showed that no treated oil was assimilated by these species. Significant uptake of oil by these species from the untreated oil was observed, with depuration to pre-discharge levels within three to six weeks. In both species, the uptake of aromatic material was relatively higher than the oil composition would predict, and the uptake and depuration in M. arenaria was faster than in M. edulis.

Although direct comparison of the results of the two experiments is not possible, certain similarities are apparent. Both experiments indicate that although rapid uptake of hydrocarbons was observed, depuration to near background levels also occurred in a short time. The apparent preference for aromatic hydrocarbons was also observed in both experiments. Neither experiment was able to distinguish between the possible mecha- nisms of this preference; preferential uptake of aromatic hydrocarbons and preferential degradation or depuration of aliphatic hydrocarbons will generate the observations. These observations are consistent with those of Rice et al. (1984) that aromatics accumulate in tissues more readily than do aliphatic hydrocarbons.

The arctic location of the present experiment may have a significant effect on the results. Owens et al. (1987) show that the fate of stranded oil on the beach in this experiment can be related to temperate situations by considering the open water periods only. This means that the input to the subtidal regime in the Arctic may continue for a much longer period than would occur in temperate climates, providing a continued source of potentially toxic hydrocarbons to the benthic communities at the time of greatest growth. This chronic stress may be more harmful than an acute stress in temperate waters.

CONCLUSIONS

Dispersed oil reached the benthic community and was rapidly taken up by the biota. Filter feeders absorbed oil more rapidly than deposit feeders, but both types did accumulate oil. Some animals appeared to have a defense mechanism in the presence of high concentrations of hydrocarbon and did not accumulate as much oil as those exposed to lower concentrations. In vivo degradation occurred, with apparently different rates in different species. The biota affected by the dispersed oil degraded or depurated most of the oil within one year.

The surface untreated oil did not reach the benthic community immediately and was not taken up by the biota. The oil stranded on the beach provided a long-term low-level chronic input to the biota.

ACKNOWLEDGEMENTS

The authors acknowledge the BIOS Project managers Peter Blackall and Gary Sergy, of the Environmental Protection Service (Environ- ment Canada), for their support and tireless efforts on behalf of the program. The guidance of the BIOS Chemistry Technical Committee and, in particular, its chairman Walter Cretney, of the Institute of Ocean Sciences, Sidney, B.C., is greatly appreciated. The assistance of other BIOS team members, especially members of the Seakem Oceanography Ltd. and LGLLtd. field teams and the Energy Resources Company Inc. laboratory staff, is also appreciated.

REFERENCES

ATLAS, R.M., HOROWITZ, A., andBUSDOSH, M. 1978. Prudhoe crude oil in arctic marine ice, water, and sediment ecosystems: Degradation and interactions with microbial and benthic communities. Journal of the Fisheries Research Board of Canada 35:585-590.

BOEHM, P.D. 1981. Chemistry 2. Hydrocarbon chemistry - 1980 study results. Baffin Island Oil Spill Working Report 80-2. Ottawa: Environmental Protection Service, Environment Canada. 184 p.

-. 1982. Chemistry 2. Analytical biogeochemistry- 1981 study results. Baffin Island Oil Spill Working Report 81-2. Ottawa: Environmental Protec- tion Service, Environment Canada. 354 p.

-. 1983. Chemistry 2. Analytical biogeochemistry- 1982 study results. Baffin Island Oil Spill Working Report 82-2. Ottawa: Environmental Protec- tion Service, Environment Canada. 210 p.

-, BARAK, J.E., FIEST, D.L., and ELSKUS, A. 1982. A chemical investigation of the transport and fate of petroleum hydrocarbons in littoral and benthic environments: The Tsesis oil spill. Marine Environmental Research 6:157-188.

BOEHM, P.D., STEINHAUER, D., COBB, D., DUFFY, S . , and BROWN, J. 1984. Chemistry 2: Analytical geochemistry - 1983 study results. Baffin Island Oil Spill Working Report 83-2. Ottawa: Environmental Protection Service, Environment Canada. 139 p.

BOEHM, P.D., STEINHAUER, M.S., GREEN, D.R., FOWLER, B., HUM- PHREY, B., FIEST, D.L., and CRETNEY, W. J. 1987. Comparative fate of chemically dispersed and beached crude oil in subtidal sediments of the arctic nearshore. Arctic 40 (Supp. 1):133-148.

BUCKLEY, J.R., DE LANGE BOOM, B.R., and REIMER, E.M. 1987. The physical oceanography of the Cape Hatt region, Eclipse Sound, N.W.T. Arctic 40 (Supp. 1):20-33.

BUNCH, J.N. 1987. Effects of petroleum releases on bacterial numbers and microheterotrophic activity in the water and sediment of an arctic marine ecosystem. Arctic 40 (Supp. 1):172-183.

CRETNEY, W. J., GREEN, D.R., FOWLER, B.R., HUMPHREY, B., FIEST, D.L., and BOEHM, P.D. 1987a. Hydrocarbon biogeochemical setting of the Baffin Island Oil Spill experimental sites. I. Sediments. Arctic (Supp. 1):

-. 1987b. Hydrocarbon biogeochemical setting of the Baffin Island Oil 51-65.

Spill experimental sites. 11. Water. Arctic 40 (Supp. 1):66-70.

HARDT, F.R., NORSTROM, R.J., SIMON, M., FIEST, D.L., and BOEHM, P.D. 1987c. Hydrocarbon biogeochemical setting of the Baffin Island Oil Spill experimental sites. 111. Biota. Arctic 40 (Supp. 1):71-79.

CROSS, W.E.,andTHOMSON,D.H. 1987,Effectsofexperimentalreleasesof oil and dispersed oil on arctic nearshore macrobenthos. I. Infauna. Arctic 40

CROSS, W.E., MARTIN, C.M., and THOMSON, D.H. 1987a. Effects of experimental releases of oil and dispersed oil on arctic nearshore macrobenthos. 11. Epibenthos. Arctic 40 (Supp. 1):201-210.

CROSS, W.E., WILCE, R.T., and FABIJAN, M.F. 1987b. Effects of experimental releases of oil and dispersed oil on arctic nearshore macrobenthos. 111. Macroalgae. Arctic 40 (Supp. 1):211-219.

CROTHERS, J.H. 1983. Field experiments on the effects of crude oil and dispersant on the common animals and plants of rocky sea shores. Marine Environmental Research 8:215-239.

DICKINS, D.F., THORNTON, D.E., and CRETNEY, W.J. 1987. Design and operation of oil discharge systems and characteristics of oil used in the Baffin Island Oil Spill Project. Arctic 40 (Supp. 1):lOO-108.

ELMGREN, R., HANSSON, S., LARSSON, U., SUNDELIN, B., and BOEHM,P.D. 1983.The'Tsesis'oilspill:Acuteandlong-termimpactonthe benthos. Marine Biology 73:51-65.

ENGELHARDT, F.R., and NORSTROM, R.J. 1982. Petroleum hydrocarbons in two benthic invertebrates, the urchin Srrongylocenrrotus droebachiensis and the polychaete Pectinaria granulosa. Special Studies - 1981 Study Results. Baffin Island Oil Spill Working Report 81- 10. Ottawa: Environmen-

FARKE, H., WONNEBERGER, K., GUNKEL, W., and DAHLMANN, G. tal Protection Service, Environment Canada. 81 p.

1985. The effects of oil and dispersant on intertidal organisms in field experiments with a mesocosm, the Bremerhaven Caisson. Marine Environ- mental Research 15:97-114.

FARRINGTON, J.W., WAKEHAM, S.G., LIVRAMENTO, J.B., TRIPP, B.W., and TEAL, J.M. 1986. Aromatic hydrocarbons in New York Bight polychaetes: Ultraviolet fluorescence analyses and gas chromatographylgas chromatography-mass spectrometry analyses. Environmental Science and Technology 20:69-72.

CRETNEY, W.J.,GREEN,D.R.,FOWLER,B.R.,I"PHREY,B.,ENGEL-

(SUPP. 1):184-200.


GILFILLAN, E.S., and VANDERMEULEN, J.H. 1978. Alterations in growth and physiology of soft-shell clams, Myu arennriu, chronically oiled with Bunker C from Chedabucto Bay, Nova Scotia, 1970-76. Journal of the Fisheries Research Board of Canada 35:630-636.

GILFILLAN, E.S., PAGE, D.S., HANSON, S.A., FOSTER, J.C., HOTHAM, J., VALLAS, D., PENDERGAST, E., HEBERT, S., PRATT, S.D., and GERBER, R. 1985. Tidal area dispersant experiment, Searsport, Maine: An overview. In: Proceedings, 1985 Oil Spill Conference, Los Angeles, Califor- nia. American Petroleum Institute publication no. 4385. 553-559.

GORDON, D.C., DALE, J., and KEIZER, P.D. 1978. Importance of sediment working by the deposit-feeding polychaete, Arenicola marina, on the weathering rate of sediment-bound oil. Journal of the Fisheries Research Board of Canada 35591-603.

HUMPHREY, B.,andVANDERMEULEN, J.H. 1986. Thecharacterizationof fifteen year old stranded oil. In: Proceedings of the Ninth Annual Arctic Marine Oilspill ProgramTechnical Seminar. Edmonton, Alberta, June 15-17, 1986. Ottawa: Environment Canada. 29-38. .

HUMPHREY, B., GREEN, D.R., FOWLER, B.R., HOPE, D., and BOEHM, P.D. 1987. The fate of oil in the water column following experimental oil spills in the arctic marine nearshore. Arctic 40 (Supp. 1):124-132.

HUTCHESON, M S . , andHARRIS, G.W. 1982. SublethalEffects of a Water- Soluble Fraction and Chemically Dispersed Form of Crude Oil on Energy Partitioning in Two Arctic Bivalves. Ottawa: Environment Canada. 30 p.

LINDBLOM, G.P., EMERY, B.D., and L A M , M.A.G. 1981. Aerial appli- cation of dispersants at the IXTOC I spill. In: Proceedings of the 1981 Oil Spill Conference, Atlanta, Georgia. American Petroleum Institute publication no. 4334. 259-262.

LLOYD, J.B.F. 1971a. The nature and evidential value of the luminescence of automobile engine oils and related materials. Part I. Synchronous excitation of fluorescence emission. Joumal of the Forensic Science Society 11:83-94.

-. 1971b. The nature and evidential value of the luminescence of automobile engine oils and related materials. Part 11. Aggregate luminescence. Journal of the Forensic Science Society 11:153-170.

-. 1971c. The nature and evidential value of the luminescence of automobile engine oils and related materials. Part 111. Separated luminescence.

MAGEAU, C., ENGELHARDT, F.R., GILFILLAN, E.S., and BOEHM, P.D. Journal of the Forensic Science Society 11:235-253.

1987. Effects of short-term exposure to dispersed oil in arctic invertebrates. Arctic 40 (Supp. 1):162-171.

NEFF, J.M., and ANDERSON, J.W. 1981. Accumulation and release of petroleum hydrocarbons. In: Response of Marine Animals to Petroleum and Specific Petroleum Hydrocarbons. London: Applied Science Publishers.

NICHOLS,J.A.,andPARKER,H.D. 1985.Dispersants:Comparisonoflabora- tory tests and field trials with practical experience at spills. In: Proceedings, 1985 Oil Spill Conference, Los Angeles, California. American Petroleum Institute publication no. 4385. 421-427.

93-142.

161

OWENS, E.H., HARPER, J.R., ROBSON, W., and BOEHM, P.D. 1987. Fate and persistence of crude oil stranded on a sheltered beach. Arctic 40 (Supp.

PAGE, D.S., FOSTER, J.C., HOTHAM, J.R., PENDERGAST, E., HEBERT, S., GONZALEZ, L., GILFILLAN, E.S., HANSON, S.A., GERBER, R.P., and VALLAS, D. 1983. Long-term fate of dispersed and undispersed crude oil in two nearshore test spills. In: Proceedings, 1983 Oil Spill Conference, San Antonio, Texas. American Petroleum Institute publication no. 4356.

PERCY, J.A. 1976. Responses of arctic marine crustaceans to crude oil and oil tainted food. Environmental Pollution 10:155-162.

PHILLIPS, D.J.H. 1980. QuantitativeBiologicalIndicators. PollutionMonitor- ing Series. London: Applied Science Publishers Ltd. 488 p.

RICE, S.D., MOLES, D.A., KARINEN, J.F., KORN, S . , CARLS, M.G., BRODERSEN, C.C., GHARRETT, J.A., and BABCOCK, M.M. 1984. Effects of petroleum hydrocarbons on Alaskan aquatic organisms: A compre- hensive review of all oil-effects research on Alaskan fish and invertebrates conducted by the Auke Bay Laboratory, 1970-1981. NOAA Technical Memorandum NMFS F/NWC-67. U.S. Department of Commerce. 127 p.

ROESUADI,G., ANDERSON, J.W., andBLAYLOCK, J.W. 1978. Uptakeof hydrocarbons from marine sediment contaminated with Prudhoe Bay crude oil: Influence of feeding type of test species and availability of polycyclic aromatic hydrocarbons. Joumal of the Fisheries Research Board of Canada

SERGY, G.A., and BLACKALL, P.J. 1987. Design and conclusions of the Baffm Island Oil Spill h j e c t . Arctic 40 (Supp. 1):l-9.

SNOW, N.B., CROSS, W.E., GREEN, R.H., and BUNCH, J.N. 1987. The biological setting of the BIOS site at Cape Hatt, N.W.T., including the sampling design, methodology and baseline results for macrobenthos. Arctic

THOMSON, D.H. 1982. Marine benthos in the eastern Canadian High Arctic; multivariate analysis of standing crop and community structure. Arctic

-,MARTIN,C.N.,andCROSS,W.E. 1987.Identificationandcharacter- ization of arctic nearshore benthic habitats. Canadian Technical Report. Fisheries and Aquatic Sciences. In press.

TJESSEM,K.,PEDERSEN,D.,andAABERG,A. 1984.Ontheenvironmental fate of a dispersed Ekofisk crude oil in sea-immersed plastic columns. Water Research 18:1129-1136.

WAKEHAM, S.G. 1977. Synchronous fluorescence spectroscopy and its appli- cation to indigenous and petroleum derived hydrocarbons in lacustrine sediments. Environmental Science and Technology 11:272-276.

WARNER, J.S. 1976. Determination of aliphatic and aromatic hydrocarbons in marine organisms. Analytical Chemistry 48578-583.

WELLS, P.G., and PERCY, J.A. 1985. Effects of oil on arctic invertebrates. Chapter 4. In: Engelhardt, F.R., ed. Petroleum Effects in the Arctic Environment. London: Elsevier Applied Science Publishers. 101-156.

1):109-123.

465-47 1.

35608-614.

40 (SUPP. 1):80-99.

35:61-74.

the fate of chemically dispersed and untreated crude oil

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